Described in RU, C1, 2017993 is a method of operating a two-stroke engine, which comprises compressing and combusting a fresh charge in a cylinder as a piston ascends towards the top dead centre, expanding combustion products in the cylinder as the piston moves away from the top dead centre, exhausting spent gases from the cylinder through an exhaust port uncovered by an upper edge of the piston, an exhaust passage and a slide valve into an exhaust pipe, scavenging and filling the cylinder with a compressed fresh charge passing through a scavenging port as the piston approaches the bottom dead centre, wherein when the piston is near the bottom dead centre, the slide valve disconnects the exhaust passage and the exhaust pipe and connects them after the cylinder has been scavenged and filled.
A problem with the above method is its poor specific characteristics due to a low degree of filling the cylinder and the great thermal stress suffered by the piston, the exhaust ports and the exhaust system as a whole.
Another conventional method of operating a two-stroke internal combustion engine comprises compressing and combusting a fresh charge in a cylinder as a piston ascends towards the top dead centre, expanding combustion products in the cylinder as the piston descends from the top dead centre, exhausting spent gases from the cylinder through an inlet-outlet port uncovered by an upper edge of the piston, an inlet-outlet passage and a slide valve into an exhaust pipe, scavenging and filling the cylinder with a compressed fresh charge passing through a scavenging port when the piston approaches the bottom dead centre, wherein when the piston is near the bottom dead centre, the inlet-outlet passage is disconnected by the slide valve from the exhaust pipe and connected through the slide valve with the inlet pipe (see US, A1, 5081961). As compared to the prior art mentioned first, the method increases the degree of filling the cylinder owing to the improved time-to-section ratio of the inlet gas distribution elements. This effect is achieved owing to the fact that the exhaust passage and port, upon performing their primary function, i.e. exhaust, act as the inlet elements. The thermal stress of the engine components is also reduced owing to cooling by the fresh charge.
The aforementioned measures, however, are insufficient to provide the highest specific parameters possible. Furthermore, the prior art embodiment having two slide valves fails to take advantage of the significant prospects of improving the time-to-section as compared to the embodiment having a single slide valve, described in the same reference.
SU, A1, 56419 discloses a two-stroke internal combustion engine comprising a crankcase with a crankshaft installed therein, at least one cylinder connected to the crankcase, a piston mounted within the cylinder and kinematically connected to the crankshaft, the cylinder having a scavenging port communicating with a compressed fresh charge source and an inlet-outlet port communicating with an inlet-outlet passage, a slide valve being mounted within the inlet-outlet passage to alternately connect the passage with an inlet pipe and an exhaust pipe.
The above engine suffers the same problems as the conventional operation methods.